You should make a LazySeq to momoize intermediate result:
(defn fib[n]
(if (> n 2)
(+ (fib (- n 2)) (fib (- n 1)))
1))
(def fib (memoize fib))
(def fib-seq (map fib (iterate inc 0)))
then take the result by nth:
user=> (nth fib-seq 45)
1134903170
user=> (nth fib-seq 46)
1836311903
user=> (nth fib-seq 47)
2971215073
The only problem is that the fib-seq would cosume more memories to
hold intermediate result.
On Jul 22, 5:47 am, logan <[email protected]> wrote:
> Lets say I have the following function
>
> (defn fib[n]
> (if (> n 2)
> (+ (fib (- n 2)) (fib (- n 1)))
> 1))
>
> and I want to memoize it, what is the right way to do it?
>
> Using the default memoize does not work correctly. the reason is even
> though the first call to fib is memoized, the recursive calls go to
> the original fib, and not the memoized function.
>
> Even using
>
> (def fib (memoize fib))
>
> does not seem to work. if you run (fib 45) and (fib 46), in the ideal
> case, (fib 47) should just call the memoized (fib 45) and (fib 46) and
> return almost immediately, but that is not the case.
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